1. Field of the Invention
The present invention relates to a breathing apparatus, and more particularly to a changeover valve that allows a user of a breathing apparatus to switch between sources of air or other gas.
2. Description of Related Art
Firefighters, military or emergency response personnel, or others may be required to work in an environment containing harmful and possibly fatal air-born toxins or other material. Respiratory hazards may include harmful gases, vapors, or particulate matter. To reduce the inhalation of harmful material, workers in such an environment may use a breathing apparatus.
One type of breathing apparatus, known as a Powered Air Purifying Respirator (PAPR), is a fan-forced positive pressure breathing apparatus. Such an apparatus may include a gas mask, a filtering element to filter potentially contaminated air, and a fan or blowing element. The fan or blowing element continually supplies filtered air to the gas mask. The filtered air replenishes the internal confines of the mask and is continually ejected.
PAPRs are typically useful in environments where the ambient air is relatively oxygen-rich and where filtering elements are effective in removing all contaminants. However, such a breathing apparatus may not be suited to environments where the ambient air is oxygen-poor or contains contaminants that cannot be filtered out. Furthermore, the filtering element becomes full of contaminants over time and must be replaced. A worker may risk exposure to hazardous or toxic materials by changing the filtering element while working in a hazardous environment.
Another type of breathing apparatus, known as a Self-Contained Breathing Apparatus (SCBA), uses a supply of air or other gas, such as a tank of compressed air. Such an apparatus may also include a gas mask and a regulator. The regulator controls the delivery of gas from the supply to the gas mask.
SCBAs are typically useful in environments where the ambient air is oxygen-poor or when there is a risk that filtering may not remove all possible contaminants. However, the source of air or other gas becomes exhausted over time and must be replaced. For this reason, it may be advantageous to use filtered air when possible. Furthermore, when the source of air or other gas becomes exhausted, a worker may risk exposure to hazardous or toxic materials by changing the source of air or other gas while working in a hazardous environment.
Furthermore, in some situations, the type of environmental contaminants may not be known in advance or may change quickly. In such a situation, a worker may be ill-equipped for a particular environment, or may risk exposure by switching from one type of breathing apparatus to another.
There is a need for a breathing apparatus that allows a worker to perform maintenance on the apparatus, such as changing a filter or replacing a source of air or other gas, while minimizing the risk of contamination. There is a further need for a system that allows a worker to quickly select an air or gas supply that is appropriate to the environment.